White Thermal Coating
AZW-LA-II / Z93 White Thermal Control Coating
White thermal control coatings, such as AZW-LA-II and Z93, are inorganic surface coatings composed of zinc oxide pigment in a potassium silicate binder, applied to aluminum substrates for sun-side passive cooling without power consumption. They maintain a solar absorptance between 0.15 and 0.20 and an infrared emittance between 0.85 and 0.92, producing an absorptance-to-emittance ratio of approximately 0.2 for radiator surfaces. The lunar ultraviolet and radiation environment actively ages exposed surfaces, necessitating inorganic formulations to resist optical degradation over a 25-year operating lifetime while periodic absorptance and emittance measurements track performance decay for robotic maintenance.
Inorganic white thermal control coating (AZW-LA-II, Z93, S13G-LO) with low solar absorptance and high IR emittance for sun-side passive cooling.
Purpose
Inorganic white thermal control coating (AZW-LA-II, Z93, S13G-LO) with low solar absorptance and high IR emittance for sun-side passive cooling.
Context
Child of L2-PTC-COAT within the Lunar Ark system
Principles
- ▸Inorganic pigments (ZnO) provide UV and radiation resistance
- ▸Solar absorptance alpha = 0.15-0.20
- ▸IR emittance epsilon = 0.85-0.92
- ▸Ratio alpha/epsilon ~0.2 for radiator surfaces
- ▸Long-life durability proven on multi-decade missions
Typical implementations
- ▸AZ Technology AZW-LA-II coating (heritage)
- ▸IITRI Z93 white coating (Apollo, ISS)
- ▸S13G-LO methylsilicone-bound ZnO
Lunar considerations
- ▸Lunar UV environment ages coatings — inorganic preferred
- ▸Periodic alpha/epsilon measurement informs degradation tracking
- ▸Robotic re-application or replacement panel via L1-MNT
Specifications
Functional
| primary function | Inorganic white thermal control coating (AZW-LA-II, Z93, S13G-LO) with low solar absorptance and high IR emittance for sun-side passive cooling. |
| alpha solar | 0.18 |
| epsilon ir | 0.88 |
Physical
| mass kg | 10 |
| materials | ZnO pigment, Potassium silicate binder, Aluminum substrate |
| vacuum compatibility | True |
Operational
| power consumption w | 0 |
| thermal range c | -40, 70 |
| lifetime years | 25 |
| mtbf hours | 1000000 |
Interfaces
Provides
- Radiator surface property
Requires
- Coating production
- Periodic refurbishment
Cite this entry
Lunar Ark Codex. "White Thermal Coating" (L3-PTC-COAT-WHITE). Retrieved 10 September 2026, from https://lunarark.com/entry/L3-PTC-COAT-WHITE
Licensed CC-BY-SA 4.0. You may reuse and adapt this entry with attribution, under the same licence.